Speckled Wood

The Speckled Wood, Pararge aegeria

The Speckled Wood is a brownish butterfly of woodland paths and glades, perching low on leaves either side of paths and edges, fluttering up when disturbed. Depending on season and wear it can either be surprisingly colourful, or on the other hand, surprisingly dull!

Description

Although on first sight the Speckled Wood is a light brown spotted and streaked butterfly of woodlands, and in the south, of large dense hedgerows, on closer examination the pattern of colours is both subtle and beautiful, giving the impression of varying textures in different areas of the wings:

Photographed at Holborough Marshes, Snodland, the 12th of May, 2014.

Distribution

Any small piece of woodland, or a path with shaws of trees on either side, can hold Speckled Woods. The males are easy to see, holding their territories, and hopefully at least some females will pass by them all, wherever they are!

Photographed at Trosley Country Park, the 17th of July, 2013.

The sex-ratio is likely to be roughly equal, but the males are much more easily noticed as they perch or patrol, while the females spend the most of their time skulking and hiding in the foliage of trees and bushes.

There is a fairly consistent daily activity pattern, and individuals tend to go to roost overnight as the sun falls, wings closed, on the underside of leaves, perhaps fairly high in the canopy. As the sun rises, it becomes necessary to bask, wings open on the upper surface of the leaves, until a body temperature of 32-35 C is reached, when the wings tend to be closed again to reduce the heat-gain.

In the summer there is plenty of honeydew on the leaves and many of the butterflies feed off this energy source. Later in the season there is less honeydew and the Speckled Wood individuals around then are more likely to be found nectaring off quite a wide range of flowers.

Individual males may be either “perchers” or “patrollers” and differ in physical shape and colouring according to their preferred mating strategies.

Life cycle

This lovely butterfly has two or possibly three generations in a particular year, a spring generation March to May, a summer generation over quite a long period, June to September, peaking about late August and a probable small third generation in October. Whether caterpillars about to pupate in the summer do form that third generation or not appears to depend largely on day-length, secondarily on temperature, but also on the genetics of that particular population.

Overall you can therefore see Speckled Wood adults for a total of eight or more months in a year, although any one individual adult probably only lasts a week or so.

Over-wintering is optional in form – either as a caterpillar or a chrysalis, and this is the only UK butterfly species that has this degree of variability in its life cycle. Both choices result in the spring-flying generation, but those individuals that over-winter as chrysalises fly earlier, and those individuals that over-winter as caterpillars fly later.

Females emerge with their eggs only partially mature and usually mate within a few hours. They then have to rest discretely while their eggs develop fully. The eggs are laid singly on clump-forming grasses such as False Brome, Cocksfoot and Yorkshire Fog. The ideal plant is a small isolated grass clump at about 24-30 C, so this is likely to be on the edge of a wood in the spring or autumn, but a shadier and thereby cooler spot inside a wood in the heat of summer.

After the egg has hatched (usually a week to a week and a half) the small caterpillars rest on the underside of the leaf nibbling gradually away at the leaf tissue.

Earlier in the year, pupation takes about ten days for the adult butterflies to emerge.Later, as the year closes down, caterpillars can hibernate in that stage, or pupate, and hibernate in that stage.

Oddities

The wings of the males are asymmetric in a complex genetically controlled manner, thought to be connected to the requirements of the spiralling flight of the males when fighting over territory.

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